Terminal blocks are used in a number of electronic systems for connecting wires, conduit, jumpers, shunts, board-to-board cables, and/or other such components to a printed circuit board. In the fabrication of HVAC controllers, for example, terminal blocks are often used to permit an installer to quickly connect wires or other components to an internal circuit board, reducing the time necessary to install an HVAC system. Such devices typically include a terminal block header equipped with a number of inlet ports that can be configured to receive wire or conduit. In certain designs, the wire or conduit can be secured to the terminal block using a screw, spring clamp, quick connect, insulation displacement connection (IDC) terminal, or other suitable fastening means. The terminal block may include a number of terminal leads or posts that can be used to electrically connect the inserted wires or conduit to attachment pads formed on the printed circuit board. The configuration of the terminal leads will typically vary depending on how the terminal block is to be mounted to the printed circuit board. If, for example, the terminal block is designed for mounting to the printed circuit board using through-hole technology (THT), the terminal leads or posts will typically have a straight configuration at their ends, although other variations do exist.
Due to their relatively large size and strength requirements, terminal blocks are typically mounted to printed circuit boards using conventional mounting techniques such as THT or wave soldering, where the terminal leads or posts are inserted through several small holes formed in the printed circuit board and then soldered in place either manually by hand or with the aid of automation equipment. A more efficient way to mount components to the printed circuit board uses surface mount technology (SMT). In SMT, components are typically mounted by soldering the component leads or terminals to attachment pads formed on the top surface of the printed circuit board. Prior to mounting, a solder paste is applied to selective portions of the printed board in a pattern corresponding generally to the attachment pads of the components. Once applied, the components are then placed onto the surface of the printed circuit board and soldered in place by applying heat. A cleaning step may then be performed on the surface of the printed circuit board to clean the lead contacts, if necessary.
While the use of SMT components is becoming increasingly popular in the art, the connection of terminal blocks using SMT still remains a significant obstacle in the manufacturing and assembly of many electronic devices. In some cases, the relatively large size of the terminal block in comparison to other SMT components may prevent the terminal block from being mounted to the printed circuit board using automated SMT techniques, thus requiring more costly hand placement methods. In addition, the force requirements that the terminal block must sustain during use may also limit the use of certain SMT techniques. As a result, the terminal blocks are often mounted to the printed circuit board subsequent to surface mounting of the other components, requiring additional manufacturing steps and/or cost. With some terminal blocks, this means manually mounting the terminal block to the printed circuit board using THT or other such methods, requiring the formation of custom footprints, hole diameters, and complicated reflow curves that can increase manufacturing time and decrease quality.
Moreover, since the terminal blocks are typically mounted on the same side of the printed circuit board as the other SMT components, there is an increased risk of electrostatic discharge and/or mechanical damage to the sensitive SMT components. For example, in some cases the use of a screwdriver or other such tool to connect the wires to the terminal block can result in undesired contact with the other components, sometimes causing damage to the printed circuit board or other components. Labeling of the terminal block may also be limited in certain cases since the other SMT components may occupy space that would normally be used for screen-printing labels on the printed circuit board.